Radiation process of preparing grafted elastomeric fibers wherein post-decrystallization is employed

ABSTRACT

CELLULOSE-CONTANING FIBROUS MATERIALS SUCH AS RAYON YARN ARE CONVERTED INTO ELASTIC MATERIALS BY A PROCESS IN WHICB THE FIBROUS MATERIALS ARE IRRADIATED, AN ACRYLATE MONOMER IS GRAFT COPOLYMERIZED ONTO THE IRRADIATED MATERIAL AND THE PRODUCT OF THE GRAFTING PROCESS IS TREATED WITH A DECRYSTALLIZING AGENT. THE ELASTIC PRODUCT OBTAINED POSSESSES GOOD EXTENSIBILITY AND ELASTIC RECOVERY AND CAN BE USED IN PALCE OF FIBROUS RUBBER IN THE PREPARATION OF ELASTIC PRODUCTS.

United States Patent 3,814,676 RADIATION PROCESS OF PREPARING G RAFTEDELASTOMERIC FIBERS WHEREIN POST-DE- CRYSTALLIZATION IS EMPLOYED Joel L.Williams, Cary, and Vivian T. Stannett, Raleigh, N.*C., assignors to J.P. Stevens & Co., Inc., New York, N.Y. No Drawing. Filed Oct. 7, 1971,Ser. No. 187,505 Int. Cl. Blllj 1/10, N12 US. Cl. 204-15912 6 ClaimsABSTRACT OF THE DISCLOSURE Cellulose-containing fibrous materials suchas rayon yarn are converted into elastic materials by a process in whichthe fibrous materials are irradiated, an acrylate monomer is graftcopolymerized onto the irradiated material and the product of thegrafting process is treated with a decrystallizing agent. The elasticproduct obtained possesses good extensibility and elastic recovery andcan be used in place of fibrous rubber in the preparation of elasticproducts.

The present invention relates to a method of imparting elasticproperties to fibrous cellulose-containing materials by graftingacrylate compounds thereon.

Heretofore, acrylate monomers such as ethyl acrylate have beenco-polymerized onto rayon for the purpose of producing elastic fibers,However, such efforts have either been unsuccessful or have achievedelasticity only after very large amounts of ethyl acrylate have beengrafted onto the rayon.

An article by Nakamura et a1. entitled, Elastomers Based on CelluloseFibers, Journal of Polymer Science, Part C, Number 23, pp. 629-645,1968, discloses grafting ethyl acrylate onto rayon fibers using cericion initiation and indicates that high graft levels are required toobtain elasticity. The use of a pretreatment with a zinc chloridedecrystallizing agent increases the elasticity at a given graft level tosome degree, but still an extent of grafting of over 1000 percent wasrequired to obtain rubber-like behaviour. In a subsequent article byNakamura et al., entitled Rheological Properties of Elastomers Based onCellulose Fibers, Polymer Preprints, Vol. 11, Number 1, February 1970,Division of Polymer Chemistry, A.C.S., work is described wherein rayonyarn is irradiated prior to grafting ethyl acrylate thereon. Thisprocess increases the elasticity of the grafted product but still, evenat high irradiation dosages, a graft level of about 300 percent wasrequired to obtain an elastic fiber.

In accordance with the present invention an elastic fibrous material isprovided by grafting an acrylate compound onto a cellulose-containingfibrous material using a procedure by which the elasticity can beobtained when the extent of grafting is as low as 50 percent by weightbased on the weight of the fibrous material. In this process thecellulose-containing fibrous material is irradiated, there is graftedonto the irradiated material an acrylate compound of the formula where Ris hydrogen or methyl and R is alkyl of 1 to 6 carbon atoms;

and the product of the grafting step is treated with a decrystallizingagent for the cellulose-containing fibrous material.

The irradiation treatment ise carried out by exposing thecellulose-containing fibrous material to high energy irradiation such asgamma rays from cobalt-60. The dose 3,814,676 Patented June 4, 1974 iceof irradiation given to the cellulose-containing fibrous material shouldbe from about 0.1 to megarads with a dose of 0.2 to 50 megarads beingpreferred. It is preferable to carry out the irradiation whilemaintaining the cellulose-containing fibrous material under vacuum, butirradiation can be carried out under atmospheric conditions. Theirradiation decreases the degree of polymerization of the cellulose inthe fibrous material with increasing irradiation dosages giving greaterdepolymerization and an increase in the elasticity of the final product.The dose should be limited to about 100 megarads to prevent excessivedegradation of the cellulose. The irradiation forms radicals in thecellulose which are capable of initiating grafting in the subsequentgrafting step.

Grafting is carried out using an aqueous emulsion of an acrylatecompound of the above given formula. Preferably the emulsion containsabout 1 to 60 percent by weight of the acrylate compound and 40 to 99percent by weight of water. Other additives may be present such as up to5 percent by weight of a dispersing or emulsifying agent. Illustrativeof suitable acrylate compounds are methyl acrylate, ethyl acrylate,propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate and thecorresponding methacrylates. Mixtures of these compounds can also beemployed. To obtain elastic properties, the extent of grafting should beequal to at least 50 percent, preferably 100 percent, by weight based onthe weight of the original cellulose-containing fibrous material.

Following the grafting step, the product is treated with adecrystallizing agent for the cellulosic material. Illustrative ofdecrystallizing agents are zinc chloride, cupriethylene diamine,cupritetramine hydroxide, concentrated liquid ammonia, lithiumhydroxide, benzyltrimethylammonium hydroxide, ethylamine andethylenediamine. Where the decrystallizing agent is a solid material itcan be used in a concentrated solution in a solvent such as water.

In order to obtain elastic material at low levels of grafting, it isessential that the treatment with the decrystallizing agent be carriedout after grafting. When the decrystallizing agent is used prior tografting, the cellulose recrystallizes during the grafting step andlittle improvement in elasticity is obtained. It is believed that thelarge increase in elasticity obtained by treatment after grafting(post-decrystallization) is a result of the grafted material preventingor interfering with recrystallization. Although the best results areobtained with a fibrous cellulose-com taining material which has beenirradiated, the use of the above-described post-decrystallization is notlimited to irradiated material. When a high extent of grafting isdesirable or permissible, post-decrystallization can be used to giveimproved results where the cellulose-containing material has not beenirradiated and the grafting of the acrylate compound has been initiatedby other means such as chemical means, e.g., ceric ion initiation.

'Ihe cellulose-containing fibrous material can be in the form of fibers,filaments or yarns, or fabrics made therefrom. The cellulose can be fromany source, including such natural sources as seed fibers such ascotton; bast fibers such as flax (linen); ramie, jute and hemp, as wellas regenerated cellulose such as rayon where wood may serve as thesource of cellulose.

The products obtained by the present invention possess goodextensibility as measured by elongation at break and good elasticrecovery. The products can be used in place of fibrous rubber in thepreparation of elastic products.

The following examples are given to further illustrate the invention,but it is understood that the invention is not to be limited in any wayby the details described herein.

3 4 EXAMPLE 1 Samples of various types of rayon yarn weighing 100Percent brealnng elongation milligrams each were wound on three-prongglass tares Percent gf i g f 70% and placed into glass ampoules.Subsequently, Itlhe am- Sample graft; z i n cuene, ZnClg oules wereevacuated at lmm. Hg. for 16 ours at 5 55 C. and sealed under vacuum.The samples were then gfi t fiigfifffijjjjjjj: gig :18 288 gg irradiatedin a cobalt 60 facility at dose rates of 0.1-0.2 megarads per hour at 25C. Following irradiation degassed emulsions of 55 millimols ethylacrylate (EA) EXAMPLE 5 and 19.0 ml. of an aqueous 5% solution of analkyl aryl hi example illustrates the use of pestdeerys- Polyetheraieohol emulsifier were added to each p tallization to improve elasticproperties where the cellu- The Samples in Contact with the graftingSolution were lose-containing material Was not irradiated. Samples ofPlaced into a water bath maintained at and grafting a continuousfilament viscose rayon yarn (150 denier, was allowed to proceed for thetimes indicated with slight 40 fil id l), wound without tension on athreeagitetion- Following the grafting Period the Samples were prongedglass bobbin, were placed in a test tube containwashed in at least threechanges of water and then soxhlet i th ifi d tit of C (NH (NO= 6H Oextracted with acetone for 8 hours to assure complete i i i 10 illi lHNO d enough water t give removal of homopolymers- 100 gms. of the finalgrafting solution. The system, main- Post-decrystallization was carriedout by exposing the m d at 35 C, was purged with N fo 30 min, nd graftedyarn to 70% aqueous ZnCl at 60 C. for 30 during the last ten minutes ofthis time, ethyl acrylate, m t s followed y thorough washing with Waterand contained in a burette inserted in the system, was simuldrying in aVacuum oven at Cupriethyiene diamine taneously purged. The ethylacrylate was added to the for minutes at foiiowed y water reaction andgrafting was continued for the time specified washing and drying wasalso used in parallel p y with the bubbling of nitrogen being maintainedfor the tallizatiou experiment 25 entire grafting time. Upon removal ofthe samples from The Peieeht graft, based on initial Sample weight, wasthe graft solution they were washed several times with calculated andthe breaking extensions determined on an tap water, then the acetone toremove h b of h 1115mm table model tester Sing a crosshead Speed ofhomopolymer. Soxhlet extraction of the rewound samples 2 in./mkn. at 21C. and 65% RH.

Percent breaking elongation Dose rate Grafting Before Dose (Mrads/ timePercent deerystah 70% Rayon t (Mrads) hr. (hrs) graft lization Cuene.ZnCl Sifiihififiiifififih hfififiihittai" 2:8 3:3 81% 15% 233 238 i 18Dnllsfanln k 11. 4 O. 1 fi .i fff filament 3,? ii; 1015 530 1410 540 500All skin 9. 7 0. 2 7. 0 179 12. 0 480 300 EXAMPLE 2 with acetone wasthen continued until constant dry sample weights were obtained. cottonyam was grafied a g i aslrayO-n Post-decrystallization of grafted yarnswas carried out m Example 1 except usmg 2 In} 5 at i ate m by exposingthe samples wound on glass bobbins to 60% 28 ml. of the 5% aqueoussolution of emulsifying agent a Z C1 1 t C f 20 Th 1 25 C. Also thetotal dose was 4.7 Mrads at a 0.1 queens n 2 i u Ion a or e es at f 2 hwere washed with water, then with 0.1% acetlc acid, and Mrads/hour rateThe grafting Period was or 4 ours finally with water and dried underreduced pressure over Sample Cotton. a mixture of CaSO /CaCl Percentgraft 192. Percent graft, and physical properties were found as Percentbreaking elongation: in Example 1.

Before decrystallization P t W t Cuene. 0 ercen I1 ima 8 7 ZnCl 400.iii-$3 ehngatmn Ce late, Time, Before Post EXAMPLE 3 Sample riib l s b ls i'ii s g r eit fi z a ti ii li z iiii h A sterilized cotton gauze padwas grafted in a similar B 0.5 31 so 590 47.6 79.2 fashion as rayon inExample 1 except using 111 millimols f g ff i 90 415 22-? 2g; of ethylacrylate and 19 ml. of the 5% aqueous solution i of emulsifying agent-Also: the P dose 42 Mrads It will be apparent that many modificationsand variaat a 0.1 Mrad/hour rate. Grafting was carried out for tions canbe fl t d Without departing f the scope hours at of the novel conceptsof the present invention, and the Samp1e Cotton gauze pad illustrativedetails disclosed are not to be construed as Percent ft 79 Imposingundue limitations on the invention. Percent breaking elongation: 5 Whatis claimed is:

B f deerystallization 35 1. In a process for imparting elasticproperties to a Queue 4 cellulose-containing fibrous material bysubjecting said 7 ZhClz 400 fibrous material to high energy radiationand graft copolymerizing onto said irradiated material at least oneEXAMPLE 4 acrylate compound of the formula: A cellophane film(regenerated cellulose) of 1.5 mils R o in thickness and a WhatmanFilter Paper No. 2. (cellu- CHpiJ-ii-Oltr lose fiber mat) were treatedin a similar fashion as exwhere ample 1 except at a total dose of 3.2Mrads and a grafting R is hydrogen or methyl and period of one hour.

R is alkyl of 1 to 6 carbon atom the improvement wherein the productobtained after said grafting is treated with a decrystallizing agent forcellulose selected from the group consisting of zinc chloride,cupriethylene diamine, cupritetramine hydroxide, concentrated liquidammonia, lithium hydroxide, benzyltrimethylammonium hydroxide,ethylamine and ethylenediamine, said process requiring an irradiationdose of about 0.1 to 100 megarads and an amount of acrylate compoundcopolymerized onto said irradiated material equal to at least 50% byweight based on the weight of said irradiated material.

2. A process as claimed in claim 1 wherein said acrylate compound isethyl acrylate.

3. A process as claimed in claim 1 wherein said cellulose-containingfibrous material is made of rayon.

4. A process as claimed in claim 1 wherein said cellulose-containingfibrous material is made of cotton.

5. A process as claimed in claim 1 wherein said decrystallizing agent isselected from the group consisting o zinc chloride and cupriethylenediamine.

6. A process as claimed in claim 1 wherein said cellulose-containingmaterial is subjected to an irradiation dose of about 0.2 to megaradsand the amount of acrylate compound graft copolymerized onto theirradiated material is equal to at least by weight based on the weightof the irradiated material.

References Cited Nakamura el al., Cellulose Graft Copolymers, I. ofApplied Polymer Science, vol. 15, pp. 391-401 (1971).

Nanamura et a1, Elastomers Based on Cellulose Fibers, J. of PolymerScience, Part C, No. 23, pp. 629-645 (1968).

JOHN C. BLEUTGE, Primary Examiner R. B. TURER, Assistant Examiner US.Cl. X.R.

8-l 16 R, 129; 260-17 A, 17.4 GC

